Controllable inflation profile balloon cover methods

ABSTRACT

A method of inflating a catheter balloon may include providing a balloon assembly operable to provide a balloon diameter vs. balloon pressure profile generally depicting a balloon inflation sequence providing at least one intermediate inflated diameter and a final inflated diameter of a balloon such that the balloon attains the at least one intermediate diameter at a predetermined pressure, and attains the final diameter at a final predetermined pressure that is lower than a predetermined pressure of a last intermediate pressure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/017,265, filed Jun. 25, 2018, which is a continuation application ofU.S. patent application Ser. No. 13/619,806 filed Sep. 14, 2012, nowU.S. Pat. No. 10,016,579, issued Jul. 10, 2018, which is aContinuation-In-Part U.S. patent application Ser. No. 13/529,896 filedJun. 21, 2012, now U.S. Pat. No. 9,370,643, issued Jun. 21, 2016, whichclaims priority to U.S. Provisional Patent Application No. 61/500,555filed Jun. 23, 2011, and also claims priority to U.S. Provisional PatentApplication No. 61/535,864 filed Sep. 16, 2011.

FIELD

This disclosure relates generally to a medical device, and moreparticularly to apparatus and a methods providing a low profile medicalballoon with controllable inflation profile.

BACKGROUND

Balloon angioplasty is a widely used procedure for expanding constrictedbody passageways, such as arteries and other blood vessels. In anangioplasty procedure, an un-inflated balloon attached to a catheter isdelivered to a constricted region of a body passageway. Once the balloonis in position at the constricted region, fluid is injected through alumen of the catheter and into the balloon. The balloon consequentlyinflates and exerts pressure against the constricted region to expandthe passageway. After use, the balloon is collapsed, and the catheter iswithdrawn.

Balloons have a number of critical design parameters. One is rated burstpressure, which is the statistically-determined maximum pressure towhich a balloon may be inflated without rupturing. In order to expandhard, calcified lesions, it is desirable that the balloon have arelatively high rated burst pressure. It is also desirable that theballoon have a low wall thickness to minimize the profile of thedelivery system when the balloon is in a deflated state. For a givenballoon material, however, there is a trade-off between burst pressureand wall thickness, in that the burst pressure generally decreases whenthe wall thickness is reduced.

Accordingly, there is a need for increasing the strength of a balloon toattain a higher rated burst pressure while maintaining a low deliveryprofile.

Balloons used for stent delivery have the added requirement ofdelivering a stent in a controlled manner. Balloons with a largedifference in their deflated profile (deflated diameter) and theirexpanded profile (expanded diameter) commonly inflate in an unevenmanner along the length of the balloon. By way of example, one end ofthe balloon may attain an expanded diameter prior to the opposing end,or the middle of the balloon may expand prior to the ends. Thisinconsistency of inflation increases the likelihood that the stent willbe dislodged longitudinally along the length of the balloon movingeither partially or fully off the balloon. The inconsistency ofinflation profile increases the likelihood for vessel trauma as thestent is unevenly expanded and subsequently unevenly engages the vesselwall.

Accordingly, there is a need in the art for a balloon system thatprovides for the control of the inflation profile to provide a uniformprofile along the length of the balloon as the system is inflated toreduce the risk of stent misalignment/dislodgement and vessel trauma.

Doctors are also commonly faced with a decision pertaining to whatdiameter stent/balloon system to choose for delivery. Accuracy inmeasurement technique and the choices in device diameter often limit thedoctor's ability to choose a balloon/stent system that is optimallysized for the intended vasculature.

Accordingly, there is a need for a balloon that provides one or moreintermediate inflated diameters that are apparent to the doctor duringdelivery that provides a uniform profile (that is, a relatively uniformdiameter) along the length of the balloon at each intermediate diameter.

SUMMARY

An embodiment comprises a catheter balloon having a working length andan expanded and an unexpanded diameter. At least partially surroundingthe balloon is a balloon cover having a length and an expanded andunexpanded diameter. Wherein said balloon cover comprises first andsecond portions, wherein said first and second portions each comprise aworking length integrally connected to a taper end having an aperturelocated at an apex of the taper end and said taper ends of said firstand second portions are located at opposite ends of said balloon coverand said first and second working lengths of the first and second coverportions overlap for a substantial portion of the balloon workinglength.

Another embodiment comprises a balloon cover having a length, anunexpanded and expanded diameter, and first and second portions, whereinsaid first and second portions each comprise a working length integrallyconnected to a taper end having an aperture located at an apex of thetaper end, and wherein said taper ends of said first and second portionsare located at opposite ends of said balloon cover and said first andsecond working lengths substantially overlap.

Another embodiment comprises a balloon cover having a length, first andsecond portions, an unexpanded and expanded diameter, and anintermediate section comprising first and second ends, wherein saidfirst and second portions each comprises a working length integrallyconnected to a taper end having an aperture located at an apex of thetaper end, wherein said taper ends of said first and second portions arelocated at opposite ends of said balloon cover and wherein said firstend of said intermediate section overlaps with the working length ofsaid first portion and the second end of said intermediate sectionoverlaps with the working length of said second portion.

Another embodiment comprises a catheter balloon assembly comprising aninflatable balloon having a balloon body portion defining a balloonworking length and an un-inflated diameter and a working diameter, and afrangible cover covering at least a portion of the balloon body portion,the frangible cover being operable to rupture under an internal pressurebefore the rupture of the balloon wherein the frangible balloon cover isoperable to control the balloon to open to an intermediate diameter thatis less than the working diameter.

Another embodiment comprises a frangible balloon assembly comprising acatheter shaft including an inflation lumen in fluid communication withan inflation port, a balloon coupled to the catheter shaft and in fluidcommunication with the inflation port, the balloon including a balloonbody portion, the balloon having a working diameter, and a frangiblecover covering at least a portion of the balloon body portion, thefrangible cover being operable to restrain the balloon to anintermediate diameter that is smaller than the working diameter up to apredetermined pressure, the frangible cover operable to rupture at thepredetermined pressure to allow the balloon to expand to the workingdiameter.

Another embodiment comprises a balloon assembly operable to provide aballoon diameter vs. balloon pressure profile generally depicting aballoon inflation sequence providing a first intermediate inflateddiameter and final inflated diameter of a balloon such that the balloonattains the first intermediate diameter at a first predeterminedpressure, and attains the final diameter at a final predeterminedpressure that is lower than the first predetermined pressure.

Another embodiment comprises a balloon assembly operable to provide aballoon diameter vs. balloon pressure profile generally depicting aballoon inflation sequence providing at least one intermediate inflateddiameter and a final inflated diameter of a balloon such that theballoon attains the at least one intermediate diameter at apredetermined pressure, and attains the final diameter at a finalpredetermined pressure that is lower than a predetermined pressure of alast intermediate pressure.

Another embodiment comprises a method of inflating a catheter balloon,comprising providing balloon assembly operable to provide a balloondiameter vs. balloon pressure profile generally depicting a ballooninflation sequence providing at least one intermediate inflated diameterand a final inflated diameter of a balloon such that the balloon attainsthe at least one intermediate diameter at a predetermined pressure, andattains the final diameter at a final predetermined pressure that islower than a predetermined pressure of a last intermediate pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments provided herein and are incorporated inand constitute a part of this specification, illustrate embodiments, andtogether with the description serve to explain the principles of theembodiments.

FIGS. 1A and 1B are top plane views of a balloon catheter and ballooncover, in a deflated and inflated state, respectively, in accordancewith an embodiment;

FIG. 2 is a side view of a medical balloon;

FIG. 3A is a side cross-sectional view of a catheter shaft, a balloonand a balloon cover in accordance with an embodiment;

FIGS. 3B and 3C are a partial cross-sectional view and an end view,respectively, of a balloon and a balloon cover having an aperturelocation relative to a balloon taper portion, in accordance with anembodiment;

FIGS. 3D and 3E are a partial cross-sectional view and an end view,respectively, of a balloon and balloon cover having an aperture locationrelative to a balloon taper portion different than the embodiment ofFIGS. 3B and 3C, in accordance with an embodiment;

FIG. 4 is a perspective view of a mandrel used to form balloon coverportions in accordance with an embodiment;

FIG. 5 is a perspective view of a mandrel used to form balloon coverportions further showing a manufacturing aid in accordance with anembodiment;

FIGS. 6A through 6E are front, right, rear, left and top plane views,respectively, of a mandrel and a film lay-up strap in accordance with anembodiment;

FIGS. 7A and 7B are top plane views, respectively, of a mandrel withfilm lay-up straps and an additional radial film layer in accordancewith an embodiment.

FIG. 8A is a perspective view of a first cover portion and a secondcover portion in accordance with an embodiment;

FIG. 8B is a perspective view of a first legged cover portion and asecond legged cover portion in accordance with an embodiment;

FIGS. 9A through 9C are top, front and right side plane views,respectively, of a folded balloon cover in accordance with anembodiment;

FIGS. 10A through 10C are perspective, front and right plane views,respectively, of a folded balloon cover, depicting a bonding process, inaccordance with an embodiment;

FIGS. 11A and 11B are tabulations of burst and pull through test resultsfor covered and uncovered balloons, respectively, in accordance withembodiments;

FIG. 12A is a cross-sectional side view of a balloon cover incorporatingan intermediate cover portion, in accordance with an embodiment;

FIG. 12B is a cross-sectional side view of a balloon cover incorporatingan intermediate cover portion, in accordance with another embodiment;

FIG. 12C is a cross-sectional side view of a balloon cover incorporatingan intermediate cover portion, in accordance with another embodiment;

FIG. 12D is a cross-sectional side view of a balloon cover incorporatingan intermediate cover portion, in accordance with another embodiment;

FIG. 12E is a cross-sectional side view of a balloon cover incorporatingan intermediate cover portion, in accordance with another embodiment;

FIG. 13 is a perspective view of a first cover portion and a secondcover portion having essentially spherical taper portions in accordancewith an embodiment;

FIGS. 14A and 14B are side views of an assembly comprising a mandrel anda film lay-up strap, in accordance with an embodiment;

FIG. 15A is a balloon diameter vs. pressure profile generally depictingan inflation sequence of the balloon described in FIG. 16, in accordancewith an embodiment;

FIG. 15B is a balloon diameter vs. pressure profile generally depictingan inflation sequence of the balloon, in accordance with an embodiment;

FIG. 16A is a side cross-sectional view of a frangible balloon assemblyincluding a catheter shaft, a balloon, and a frangible balloon covercomprising a legged balloon cover and a frangible cover, in accordancewith an embodiment;

FIG. 16B is a side cross-sectional view of a frangible balloon assemblyincluding a catheter shaft, a balloon, and a frangible cover, inaccordance with an embodiment;

FIG. 16C is a side cross-sectional view of a frangible balloon assemblyincluding a catheter shaft, a balloon, and a first frangible cover, asecond frangible cover, and a third frangible cover, in accordance withan embodiment

FIG. 17A is a side view of the frangible cover in accordance with anembodiment;

FIG. 17B is a side cross-sectional view of a frangible balloon assemblyin a state of intermediate inflation wherein the frangible cover is notruptured and the diameter of the frangible balloon assembly is at anintermediate diameter, in accordance with an embodiment;

FIG. 17C is a side cross-sectional view of a frangible balloon assemblyin a state of inflation to the balloon working diameter wherein thefrangible cover has ruptured releasing the balloon to attain a finaldiameter, in accordance with an embodiment;

FIG. 17D is a side cross-sectional view of a frangible balloon assemblyin a state of intermediate inflation wherein the frangible cover is notruptured and the diameter and length of the frangible balloon assemblyis at an intermediate diameter and length, in accordance with anembodiment;

FIG. 17E is a side cross-sectional view of a frangible balloon assemblyin a state of inflation to the balloon working diameter wherein thefrangible cover has ruptured releasing the balloon to attain a finaldiameter and length, in accordance with an embodiment;

FIG. 18A is a side view of the frangible cover comprising elongatednodes, in accordance with an embodiment;

FIG. 18B is a side view of the frangible cover comprising notches, inaccordance with an embodiment;

FIG. 18C is a side view of the frangible cover comprising perforations,in accordance with an embodiment;

FIG. 18D is a side view of the frangible cover comprising a seam, inaccordance with an embodiment;

FIG. 19A is a frangible cover stress strain curve, in accordance with anembodiment; and

FIG. 19B is a frangible cover stress strain curve, in accordance with anembodiment.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the embodiment providedherein without departing from the spirit or scope of the invention.Thus, it is intended that the present invention cover the modificationsand variations of this invention provided they come within the scope ofthe appended claims and their equivalents. Although the presentinvention may be described in connection with various principles andbeliefs, the present invention should not be bound by theory.

It should be noted that the accompanying drawing figures referred toherein are not all drawn to scale, but may be exaggerated to illustratevarious aspects of the embodiments, and in that regard, the drawingfigures should not be construed as limiting.

Described herein is apparatus and methods providing a low profilemedical balloon with controllable inflation profile.

As used herein, the term “proximal” relates to a direction that is“closest to the heart”, while “distal” relates to a direction that is“furthest from the heart”.

FIG. 1A is a side view of a catheter system 100 having a balloon 200 anda balloon cover 300, in accordance with an embodiment. The cathetersystem 100 further comprises a distal hub 102 and a catheter shaft 104.The balloon 200 is in a deflated state. The balloon cover 300 surroundsa substantial portion of the balloon 200. FIG. 1B is a side view of thecatheter system 100 of the embodiment of FIG. 1A with the balloon 200 inan inflated state. The balloon cover 300 surrounds a substantial portionof the inflated balloon 200. Also shown is a cross-sectional planedefined as “3-3” that is referenced in FIGS. 3A, 3B, 3D.

FIG. 2 is a side view of a common medical balloon 200. The balloon 200comprises two opposed balloon leg portions 204 that are each integrallyconnected to a balloon taper portion 206, with each of the balloon taperportions 206 connected to a balloon body portion 208 therebetween. Aballoon working length 210 is defined as the length of the balloon bodyportion 208 of the balloon 200 that comprises the approximate lengthbetween the opposed balloon taper portions 206. The balloon leg portions204, balloon taper portions 206, and the balloon body portion 208 definea balloon overall length.

FIG. 3A is a side cross-sectional view taken along plane 3-3 (see FIG.1B) showing various elements of the balloon 200 and balloon cover 300 inaccordance with an embodiment. Shown is a catheter shaft 104, aninflation lumen 105, and inflation ports 125 with the attached balloon200. The balloon cover 300 is positioned around the balloon taperportions 206 and the balloon body portion 208 of the balloon 200. Theballoon cover 300 comprises a first cover portion 313 and a second coverportion 315. The first cover portion 313 comprises a first cover bodyportion 312 and a first cover taper portion 314. The first cover bodyportion 312 is operable to overlay a portion of the balloon body portion208.

The first cover taper portion 314 is operable to overlay a portion ofthe balloon taper portion 206 as shown in FIG. 3A. The first cover taperportion 314 defines a first cover aperture 316 located at an apex 317 ofthe first cover taper portion 314. The first cover aperture 316 isoperable to allow the balloon leg portion 204 of the balloon 200 to passthrough.

The second cover portion 315 comprises a second cover body portion 318and a second cover taper portion 320. The second cover body portion 318is operable to overlay a portion of the balloon body portion 208.

The second cover taper portion 320 is operable to overlay at least aportion of the balloon taper portion 206 as shown in FIG. 3A. The secondcover taper portion 320 defines a second cover aperture 322 located atan apex 323 of the second cover taper portion 320. The second coveraperture 322 is operable to allow the balloon leg portion 204 of theballoon 200 to pass through.

Referring again to FIG. 3A, the first cover taper portion 314 and thesecond cover taper portion 320 are located at opposite ends of theballoon cover 300. The first cover portion 313 and the second coverportion 315 are coaxially aligned along axis X and overlay the balloon200 such that at least a portion of the first cover body portion 312overlays at least a portion of the second cover body portion 318. Theoverlay of the first cover body portion 312 and the second cover bodyportion 318 defines a cover working length 311. In the embodiment ofFIG. 3A, the working length 311 overlays a substantial portion of theballoon working length 310. A “substantial portion of the balloonworking length” is defined herein as about over 50% to about 100% of theballoon working length. In embodiments, a “substantial portion of theballoon working length” comprises over and/or about 60%, about 70%,about 80%, about 90%, about 95%, and about 98% of the balloon workinglength 210.

Shown in FIG. 3B is a partial cross-sectional side view of the firstcover portion 313 of the balloon cover 300, shown overlaying an inflatedballoon 200. The additional layers shown in FIG. 3A have been omittedfor clarity. The aperture 316 is shown positioned about 20% “up along”the balloon taper portion 206 of the balloon 200. As shown, a positionthat is “zero %” up the balloon taper portion 206 is located at ajunction of the balloon leg 204 and the balloon taper portion 206. Aposition that is “100%” up the balloon taper portion 206 is located atthe junction of the balloon taper portion 206 and the balloon bodyportion 208. FIG. 3C is an end view of the balloon 200 and a first coverportion 313. Shown is the cover aperture 316 positioned about 20% up theballoon taper portion 206 of the balloon 200. Also shown are inflatedballoon diameter 324, balloon leg diameter 326 and aperture diameter 328a. The position of the aperture 316 relative to the balloon taperportion 206 of the balloon 200 can be expressed as a ratio of aperturediameter 328 a to the inflated balloon diameter 324. Similarly, theposition of the aperture 316 relative to the balloon taper portion 206can be expressed as a ratio of aperture diameter 328 a to the balloonleg portion diameter 326.

FIGS. 3D and 3E are similar to previous FIGS. 3B and 3C. As shown inFIG. 3D, the aperture 316 is shown positioned about 75% “up along” theballoon taper portion 206 of the balloon 200. FIG. 3E is an end view ofthe balloon 200 with the surrounding first cover portion 313. Shown isan aperture 316 positioned about 75% up the balloon taper portion 206 ofthe underlying balloon 200. Also shown are inflated balloon diameter324, leg portion diameter 326 and aperture diameter 328 b. The positionof the aperture 316 relative to the balloon taper portion 206 can beexpressed as a ratio of aperture diameter 323 b to the inflated balloondiameter 324. Similarly, the position of the aperture 316 relative tothe balloon taper portion 206 can be expressed as a ratio of aperturediameter 328 b to the leg portion diameter 326. Note that FIGS. 3C and Eare not drawn to scale, but are intended to illustrate a difference inthe size of the aperture 316.

Large aperture sizes may useful for many applications including, but notlimited to, for designing a balloon fail safe so that the balloon 200will fail only in the area not covered by the balloon cover 300, such asthe balloon taper portion 206 area of the balloon (see FIG. 2) and/orfor reducing pull through forces (see below) by reducing the amount ofmaterial in the balloon taper portion 206 and thus reducing profile inthat area.

Endoluminal balloons are typically blow molded from a uniform wallthickness tube. Once molded, the tube is stretched resulting in avarying wall thickness along the length of the balloon. The balloon iscommonly thickest at the balloon leg portions 204 and becomesprogressively thinner along the balloon taper portion 206 and thethinnest at the balloon body portion 208. Thickness is inverse to thestress on the balloon while under pressure. The thinnest wall of theblow molded balloon, for example, will therefore be under the greateststress when inflated.

The balloon leg portions 204 substantially retain the thickness of theuniform wall thickness tube before blow molding the balloon body portionand the balloon taper portions and thus are commonly a wall thicknessthat is oversized for the stresses that the leg portions are likely toexperience when the balloon 200 is inflated. This extra thickness andthus the profile may increase the minimum introducer size that a balloonmay be withdrawn.

The balloon covers 300 in accordance with embodiments provided herein,cover, and therefore reinforce, the thinner portions of the balloon 200.Thus, in accordance with embodiments, a balloon cover 300 providesadditional strength to the balloon 200. In accordance with anembodiment, the thinnest part of the balloon 200 is covered by astrongest portion of the balloon cover 300 and vice versa. Embodimentsof a balloon cover 300 increases the rated burst pressure of a balloon200 with minimal addition to withdrawal profile.

Balloons and balloon covers may be fabricated from a variety of commonlyknown materials such as Amorphous Commodity Thermoplastics that includePolymethyl Methacrylate (PMMA or Acrylic), Polystyrene (PS),Acrylonitrile Butadiene Styrene (ABS), Polyvinyl Chloride (PVC),Modified Polyethylene Terephthalate Glycol (PETG), Cellulose AcetateButyrate (CAB); Semi-Crystalline Commodity Plastics that includePolyethylene (PE), High Density Polyethylene (HDPE), Low DensityPolyethylene (LDPE or LLDPE), Polypropylene (PP), Polymethylpentene(PMP); Amorphous Engineering Thermoplastics that include Polycarbonate(PC), Polyphenylene Oxide (PPO), Modified Polyphenylene Oxide (Mod PPO),Polyphenelyne Ether (PPE), Modified Polyphenelyne Ether (Mod PPE),Thermoplastic Polyurethane (TPU); Semi-Crystalline EngineeringThermoplastics that include Polyamide (PA or Nylon), Polyoxymethylene(POM or Acetal), Polyethylene Terephthalate (PET, ThermoplasticPolyester), Polybutylene Terephthalate (PBT, Thermoplastic Polyester),Ultra High Molecular Weight Polyethylene (UHMW-PE); High PerformanceThermoplastics that include Polyimide (PI, Imidized Plastic), PolyamideImide (PAI, Imidized Plastic), Polybenzimidazole (PBI, ImidizedPlastic); Amorphous High Performance Thermoplastics that includePolysulfone (PSU), Polyetherimide (PEI), Polyether Sulfone (PES),Polyaryl Sulfone (PAS); Semi-Crystalline High Performance Thermoplasticsthat include Polyphenylene Sulfide (PPS), Polyetheretherketone (PEEK);and Semi-Crystalline High Performance Thermoplastics, Fluoropolymersthat include Fluorinated Ethylene Propylene (FEP), EthyleneChlorotrifluroethylene (ECTFE), Ethylene, Ethylene Tetrafluoroethylene(ETFE), Polychlortrifluoroethylene (PCTFE), Polytetrafluoroethylene(PTFE), Polyvinylidene Fluoride (PVDF), Perfluoroalkoxy (PFA). Othercommonly known medical grade materials include elastomeric organosiliconpolymers, polyether block amide or thermoplastic copolyether (PEBAX).

Balloon covers in accordance with embodiments can be fabricated by avariety of methods such as molding, vacuum/pressure forming,film-wrapping, film-layering, fiber winding or other methods known inthe art.

The following describes an embodiment of a method of making a ballooncover utilizing thin, polymeric film lay-ups that can be used tofabricate various balloon covers in accordance with embodimentspresented herein. In accordance with an embodiment, a method comprisesthe following steps.

Fabricate a stepped metallic, film lay-up mandrel fabricated accordingto FIG. 4. Shown is a metallic mandrel 400 having a first cylindricalportion 402. The first cylindrical portion 402 has a diameter 404 and alength 406. Similarly, the metallic mandrel 400 has a second cylindricalportion 408. The second cylindrical portion 408 has a diameter 410 and alength 412. The first and second cylindrical portions 402, 408 areintegrally connected to opposing taper portions (414, 416). The opposingtaper portions (414, 416) are integrally connected to opposing shafts(418, 420), having diameters 422. The lengths (406, 412), diameters(404, 410) and taper portion (414, 416) dimensions can be tailored toaccommodate the dimensions of a subsequent underlying balloon. Lengths(406, 412) can range from about 1 mm to more than 100 mm, diameters(404, 410) can range from about 1 mm to more than 100 mm and taperportion angles can range from about 10° to about 90°. In one embodiment,the cover diameter is undersized by about at least 5% relative to theballoon diameter. Undersizing the balloon cover by at least 5% allowsthe balloon cover to bear the radial load of an inflated balloon, thusnot allowing the balloon to fail, at least in the covered region of theballoon.

Using the mandrel 400 to form a first cover portion and a second coverportion having overlapping cover body portions defining a workinglength. For the cover body portions to overlap, a first cover portion isfabricated to have a cover body portion inner diameter that is slightlylarger than the cover body portion outer diameter of the second coverportion. The difference between the cover body portion diameters isdictated by the different diameters of the first cylindrical portion 402and the second cylindrical portion 408. For example diameter 404 can beabout 0.012″ larger than diameter 410, accommodating balloon covers witha 0.006″ wall thickness.

Mount one of the shafts (418, 420) onto a rotatable collet to hold themandrel and allow rotation of the mandrel during subsequent processingsteps. As shown in FIG. 5, a manufacturing aid, in the form of a film502 coated with a thermoplastic adhesive can be added to the centerportion of the mandrel 500. For example, two to five circumferentialwraps can be applied. The layers can be secured by reflowing thethermoplastic adhesive by the application of heat, such as by asoldering iron or other heating means. The width of the film and thelocation on the mandrel can be selected to accommodate the dimensions ofdesired balloon cover portions. A suitable film can comprise expandedpolytetrafluoroethylene (ePTFE) imbibed or coated with a thermoplasticfluoroelastomer or other combinations of polymeric films andthermoplastics.

Apply a series of film layers or straps, as described in FIGS. 6Athrough 6E, onto the first cylindrical portion (larger diameter relativeto the second cylindrical portion) and onto the integrally connectedtaper portion of the mandrel. Shown in FIG. 6A is a front plane view ofa mandrel 600 with a strap of a thin polymeric film 604 positioned overa taper portion 614. Shown in FIG. 6B is a right side plane view (ofFIG. 6A) of a mandrel 600 with a strap of a thin polymeric film 604positioned over a taper portion 614. As shown, the film strap 604 isclosely abutted against the base of the integral shaft 618. Similarly,FIG. 6C is a rear side plane view (of FIG. 6A) of a mandrel 600 with astrap of a thin polymeric film 604 positioned over a taper portion 614.FIG. 6D is a left side plane view (of FIG. 6A) of a mandrel 600 with astrap of a thin polymeric film 604 positioned over a taper portion 614.Note that the width and size of the straps can vary depending on theapplication.

Smooth out and heat tack the portions of the film strap 604 to theoverlying film/thermoplastic manufacturing aid 602, resulting in onefilm strap formed onto the mandrel 600.

FIG. 6E is a top plane view (of FIG. 6A) showing the film 604 closelyabutted against the integral shaft 618. For reference, the film shown isoriented (relative to the mandrel 600) at a “zero degree” position. Twoadditional film straps can be added in a “clocked” fashion whereby thepoint where the film strap abuts the integral shaft 618 is orientedabout 120° relative to the previous film strap. The two additional filmstraps can be heat tacked to the manufacturing aid 602 resulting inthree film straps formed onto the mandrel 600.

The polymeric film used as a film strap can comprise an expandedpolytetrafluoroethylene (ePTFE) film coated on one side with athermoplastic (or thermoset) adhesive. The three film straps of FIGS. 6Athrough 6E can have the adhesive side oriented out and away from themandrel.

EPTFE may be made as taught by U.S. Pat. Nos. 3,953,566 and 4,187,390,both of which are incorporated by reference herein. In anotherembodiment, said ePTFE is impregnated with a thermoplastic (orthermoset) adhesive, silicone adhesive, silicone elastomer, siliconedispersion, polyurethane or another suitable elastomeric material.Impregnation involves at least partially filling the pores of the porousPTFE. U.S. Pat. No. 5,519,172 teaches in detail the impregnation ofporous PTFE with elastomers, such as the one taught in U.S. Pat. No.7,462,675. In an embodiment, the film comprises an elastomer so thatwhen formed into a balloon cover in accordance with an embodiment, thecover will expand and contract, thus also contracting and/or refoldingthe balloon.

A circumferentially wrapped film layer can be added to the wrappedmandrel. Shown in FIG. 7A, a mandrel 700 having a wrapped filmmanufacturing aid 702 and three polymeric film straps 704 are wrapped.As shown in FIG. 7B, a film layer 706 can be circumferentially wrappedabout the first cylindrical portion (FIG. 4, 402). The circumferentiallywrapped film layer 706 can have an end-to-end (708, 710) overlap asshown. The polymeric film used as a circumferential wrap 706 cancomprise an ePTFE film, coated on one side with a thermoplastic (orthermoset) adhesive. The circumferential wrap 706 can have the adhesiveside oriented out and away from the mandrel. The overlapping ends of thefilm can be heat tacked and bonded together.

Three additional film straps can be added to the first cylindricalportion (FIG. 4, 402). The first additional film strap can be added in“clocked” fashion whereby the point where the film strap abuts theintegral shaft 618 (FIG. 6) is oriented about 60° relative to theprevious film strap. The second and third additional film straps canthen be added in a “clocked” fashion whereby the point where the filmstrap abuts the integral shaft 618 (FIG. 6) is oriented about 120°relative to the previous film strap.

The portions of the film straps overlying the film/thermoplasticmanufacturing aid 602 (FIG. 6) can be smoothed out and heat tacked tothe manufacturing aid.

The polymeric film used as a film strap can comprise an ePTFE film,coated on one side with a thermoplastic (or thermoset) adhesive. Thethree additional film straps can have the adhesive side oriented inwardand towards the mandrel.

A circumferentially wrapped film layer can be added to the wrappedmandrel. The polymeric film used as a circumferential wrap can comprisean ePTFE film coated on one side with a thermoplastic (or thermoset)adhesive. The circumferential wrap can have the adhesive side orientedinward and towards the mandrel.

Using a process as similar to that described in FIGS. 6A through 6E, aseries of film layers or straps can be applied onto the secondcylindrical portion (smaller diameter relative to the first cylindricalportion) and onto the integrally connected taper portion of the mandrel.

Six film straps can be applied according to the process described above.The adhesive side of the film straps can be oriented out and away fromthe mandrel.

Two layers of a circumferentially wrapped film can be added to thewrapped mandrel. The circumferentially wrapped film can be appliedaccording to the process described above and can have the adhesive sideof the film straps oriented out and away from the mandrel.

The mandrel with film wrapped first and second cylindrical portions andintegrally connected taper portions can then be heat treated in an airconvection (e.g. in an over set of 250° C. for about 30 minutes). Theheat treatment reflows the thermoplastic adhesive and bonds the variousfilm layers together. The mandrel and films can then be ambient, forcedair cooled for about 30 minutes.

The bonded films on the first and second cylindrical portions andintegrally connected taper portions can then be circumferentially cutand removed from the mandrel. The location of the circumferential cutcan determine the desired first cover body portion and the second coverbody portion of the first cover portion and the second cover portion,respectively. FIG. 8A is a side perspective view of a balloon cover 300comprising a larger diameter first cover portion 313 having a firstcover body portion 312 integrally connected to a first cover taperportion 314. The first cover taper portion 314 has an aperture 316located at an apex of the first cover taper portion 314. Also shown inFIG. 8A is a smaller diameter second cover portion 315 having a secondcover body portion 318 integrally connected to a second cover taperportion 320. The second cover taper portion 320 has an aperture 322located at an apex of the second cover taper portion 320.

As further shown in FIG. 8A, the second cover portion 315 can beinserted into the first cover portion 313 by translating the second andfirst cover portions as indicated by direction arrows (820, 822), sothat the first cover body portion 312 and the second cover body portion318 are substantially overlapped. “Substantially overlapped” is definedherein as an overlap of the first and second cover body portions ofabout over 50% to about 100%. In accordance with embodiments,“substantially overlapped” comprises about 60%, about 70%, about 80%,about 90%, about 95%, about 98% of the first and second cover bodyportions defining the cover working length.

In accordance with another embodiment, the balloon cover may furthercomprise a leg portion extending from each of the cover taper portions.The leg portions are operable for receiving therein balloon leg portions204 shown in FIG. 2, for example. FIG. 8B is a side perspective view ofa legged balloon cover 300 b comprising a first legged cover portion 313b and a second legged cover portion 315 b. The first legged coverportion 313 b includes a first cover body portion 312 integrallyconnected to a first cover taper portion 314, further comprising a coverleg portion 1504 located at an apex of the first cover taper portion314. The second legged cover portion 315 b includes a second cover bodyportion 318 integrally connected to a second cover taper portion 320,further comprising a cover leg portion 1504 located at an apex of thesecond cover taper portion 320.

In preparation for bonding the first cover body portion 312 and secondthe cover body portion 318 together, the first cover portion 313 andsecond cover portion 315 are flattened-out to form a cup-shaped assembly300 a as generally depicted in FIGS. 9A through 9C. FIG. 9A is a topplane view of flattened first cover portion 313 and second cover portion315 after having been assembled such that the second cover body portion318 is overlapped by the first cover body portion 312 to the desiredamount defining the working length 902. As shown in FIG. 9A, the secondcover body portion 318 is substantially overlapped by the first coverbody portion 312. Also shown are apertures 316,322 located at apexes ofthe cover taper portions of the first cover portion 313 and second coverportion 315. FIG. 9B is a front plane view of the cup-shaped assemblyshown in FIG. 9A, while FIG. 9C is a right side plane view of thecup-shaped assembly 300 a shown in FIG. 9A.

FIGS. 10A through 10C describe a method used to bond the first coverbody portion 312 and second cover body portion 318 together. Shown inFIG. 10A is a ring 1000 having a length 902 a that approximates theworking length 902. As shown in FIGS. 10B and 10C, the ring 1000 can beinserted into the cup-shaped assembly 300 a. As shown in FIG. 10C, thering 1000 has a diameter 1010 dimensioned to mate into the cup-shapedassembly 300 a. A layer of high temperature polymeric film, such asKapton® can then be circumferentially wrapped around the ring 1000 andcup-shaped assembly 300 a after the ring 1000 is inserted into thecup-shaped assembly 300 a. A high temperature fiber can becircumferentially wrapped about the high temperature polymeric film, thering 1000 and cup-shaped assembly 300 a. When heated, the hightemperature fiber can be operable to shrink and contract about the hightemperature polymeric film and the ring 1000 and cup-shaped assembly 300a, and therefore apply pressure onto the overlapped first cover bodyportion 312 and second cover body portion 318. After securing the hightemperature fiber the components can be heated in an air convection ovento about 250° C. for about 30 minutes. The pressure applied by thecontracting high temperature fiber causes the thermoplastic layerswithin the overlapped first cover body portion 312 and second cover bodyportion 318 to reflow and form a bond between the layers.

The assembly can then be ambient forced air cooled for about 30 minutes.The high temperature fiber, high temperature film and the ring 1000 canbe removed and the bonded first and second cover portions can beexpanded to form the balloon cover 300. A compacted balloon mounted ontoa catheter can be inserted into the balloon cover 300 thereby forming acovered balloon as previously described in FIG. 3A. The balloon can beinflated to conform to the balloon cover and then can be partiallydeflated. While the balloon is partially deflated, an adhesive can beinjected into the balloon cover apertures (316, 322 of FIG. 9A) to bondthe opposing ends of the balloon cover to the underlying balloon. Theadhesive can be cured forming a catheter system having a balloon 200 anda balloon cover 300 in accordance with an embodiment, as depicted inFIGS. 1A and 1B. In an embodiment, the balloon cover 300 does not coverthe balloon leg portions 204 (see FIG. 2) of the balloon 200. In anotherembodiment, the balloon cover 300 is not attached to a catheter, or anyother structure that a balloon 200 is mounted.

The balloon cover in accordance with embodiments herein are scalable todifferent size balloons. Thus, a 24 mm to 37 mm diameter balloon withthe cover in accordance with an embodiment may have a burst pressure of9 atmospheres (atm) to 20 atm. Similarly smaller diameter balloons, e.g.a 5 mm diameter balloon can be converted to a high pressure balloon bythe addition of a balloon cover in accordance with embodiments providedherein. In an embodiment, a 29 mm balloon with a rated burst pressure of3 atm may be converted to a high pressure balloon with a burst pressureof about 11 atm with the addition of a balloon cover in accordance withembodiments provided herein. In another embodiment, a 5 mm diameterballoon may have a burst pressure of about 45 atm with the addition of aballoon cover in accordance with embodiments provided herein.

An embodiment of a balloon catheter system comprises a balloon cathetercomprising an inflatable medical balloon having a balloon working lengthand an expanded and unexpanded diameter, and a balloon cover having alength and an expanded and unexpanded diameter, wherein the ballooncover comprises a first cover portion and a second cover portion,wherein the first cover portion and second cover portion each comprise acover body portion integrally connected to a cover taper portion havingan aperture located at an apex of the cover taper portion, and whereinthe cover taper portions of the first cover portion and second coverportion are located at opposite ends of the balloon cover and the firstcover body portion and second cover body portion overlap for asubstantial portion of the balloon working length defining a coverworking length. In another embodiment, the medical balloon is anon-compliant balloon. In another embodiment, the medical balloon is acompliant balloon. In another embodiment, the balloon cover comprises afibrillated material. In another embodiment, the fibrillated material isePTFE. In another embodiment, fibrils in the ePTFE are oriented in aradial direction. In another embodiment, the balloon cover comprisesstrips of ePTFE that are adhered to each other. In another embodiment,the strips are laid in multiple angular orientations on the cover bodyportions and the cover taper portions of the balloon cover. In anotherembodiment, the balloon cover is adhered to the medical balloon. Inanother embodiment, the cover working length overlaps a portion of aballoon taper portion. In another embodiment, the expanded diameter ofthe balloon cover is smaller than the expanded diameter of the medicalballoon.

In accordance with another embodiment, a balloon cover comprises alength, an unexpanded and expanded diameter, and first and second coverportions, wherein the first and second cover portions each comprise acover body portion integrally connected to a cover taper portion havingan aperture located at an apex of the cover taper portion, and whereinthe cover taper portion of the first cover portion and second coverportion are located at opposite ends of the balloon cover and the firstand second cover body portions overlap for a substantial portion of thelength of the balloon cover.

Various alternative embodiments can be fabricated. For example,embodiments of balloon covers can incorporate additional balloon coverportions so that a balloon cover has more than two cover portions. Aballoon cover in accordance with embodiments can have two, three, four,five, six, seven, eight, nine, ten or more sequentially overlappingportions. Balloon covers can also be formed to have cover taper portionsof various lengths and/or non-circular cross-sectional profiles.Embodiments of balloon covers can also incorporate strengtheningelements such as high strength fibers, braids or other elements toenhance the balloon cover strength or rigidity. Balloon covers inaccordance with embodiments can also incorporate surface treatments toprovide drugs, therapeutic agents, lubricious coatings or radiopaquemarkings. A guidewire channel can also be provided between a balloon anda balloon cover resulting in an optional “rapid exchange” configuration.

In accordance with other embodiments, FIGS. 12A through 12E show sidecross-sectional views of embodiments of balloon covers comprising afirst cover portion 1213 and a second cover portion 1215 along withvarious intermediate cover portions. FIG. 12A is a side cross-sectionalview of a balloon cover 1200 comprising a first cover portion 1213, asecond cover portion 1215, and an intermediate cover portion 1230. Thefirst cover portion 1213 and the second cover portion 1215 areco-axially aligned and closely abutted defining a gap 1232. Theintermediate cover portion 1230 bridges the gap 1232 and is overlappedat least partially by a first cover body portion 1212 and a second coverbody portion 1218.

FIG. 12B is a side cross-sectional view of a balloon cover 1201comprising a first cover portion 1213, a second cover portion 1215, andan intermediate cover portion 1234. The first cover portion 1213 and thesecond cover portion 1215 are co-axially aligned and spaced apartdefining a gap 1235. The intermediate cover portion 1234 bridges the gap1235 and is overlapped at least partially by a first cover body portion1212 and a second cover body portion 1218.

FIG. 12C is a side cross-sectional view of a balloon cover 1202comprising a first cover portion 1213, a second cover portion 1215, andan intermediate cover portion 1236. The intermediate cover portion 1236defines a stepped diameter that is smaller than diameters of the firstand second balloon cover portions. The first cover portion 1213 and thesecond cover portion 1215 are co-axially aligned and spaced apartdefining a gap 1235. The intermediate cover portion 1236 bridges the gap1235 and is overlapped at least partially by a first cover body portion1212 and a second cover body portion 1218.

FIG. 12D is a side cross-sectional view of a balloon cover 1203comprising a first cover portion 1213, a second cover portion 1215, andan intermediate cover portion 1238. The intermediate cover portion 1238defines a stepped diameter that is larger than diameters of the firstand second balloon cover portions. The first cover portion 1213 and thesecond cover portion 1215 are co-axially aligned and spaced apartdefining a gap 1235. The intermediate cover portion 1238 bridges the gap1235 and is overlapped at least partially by a first cover body portion1212 and a second cover body portion 1218.

FIG. 12E is a side cross-sectional view of a balloon cover 1204comprising a first cover portion 1213, a second cover portion 1215, andan intermediate cover portion 1240. The intermediate cover portion 1240defines a stepped diameter that is larger than diameters of the firstand second balloon cover portions. The intermediate cover portion 1240incorporates a groove 1242 along a circumference of the intermediatecover portion 1240. The first cover portion 1213 and the second coverportion 1215 are co-axially aligned and spaced apart defining a gap1235. The intermediate cover portion 1238 bridges the gap 1235 and isoverlapped at least partially by a first cover body portion 1212 and asecond cover body portion 1218.

Balloon covers of embodiments provided herein may incorporate one, two,three, four, five or more additional intermediate cover portions. Theintermediate cover portions can have similar or dissimilar shapes orprofiles and can be configured for a specific application. For example,a stepped intermediate cover portion can be configured to expand andanchor a heart valve stent. In another embodiment the steppedintermediate cover portion can be configured to expand and anchor a veinvalve, a pulmonary valve or a non-cylindrical stent.

In accordance with another embodiment, a balloon cover is providedcomprising a length, a first cover portion and a second cover portion,an unexpanded and expanded diameter, and an intermediate portioncomprising an intermediate portion first end and an intermediate portionsecond end opposite the intermediate portion first end, wherein thefirst cover portion and second cover portion each comprise a cover bodyportion integrally connected to a cover taper portion having an aperturelocated at an apex of the cover taper portion, wherein the cover taperportions of the first cover portion and second cover portions arelocated at opposite ends of the balloon cover and wherein theintermediate portion first end overlaps with at least a portion of thecover body portion of the first cover portion and the intermediateportion second end overlaps with at least a portion of the cover bodyportion of the second cover portion.

In accordance with another embodiment, a balloon cover is providedcomprising a length, a first cover portion and a second cover portion,an unexpanded and expanded diameter, and an intermediate portioncomprising an intermediate portion first end and an intermediate portionsecond end opposite the intermediate portion first end, wherein thefirst cover portion and second cover portion each comprise a cover bodyportion integrally connected to a cover taper portion having an aperturelocated at an apex of the cover taper portion, wherein the cover taperportions of the first cover portion and second cover portions arelocated at opposite ends of the balloon cover and wherein theintermediate portion first end overlaps with at least a portion of thecover body portion of the first cover portion and the intermediateportion second end overlaps with at least a portion of the cover bodyportion of the second cover portion. In another embodiment, when theballoon cover is in its expanded diameter, the intermediate sectionconfers to the balloon cover a shape selected from the group consistingof an hourglass, triangular, square, rectangular, oval or other polygon.In another embodiment, the intermediate section comprises a differentmaterial than the first cover portion and second cover portion. Inanother embodiment, the intermediate section comprises ePTFE.

It is understood that the cover taper portions may define any suitableshape complementary to the shape of an inflated balloon. Referring againto FIG. 8A, the first cover taper portion 314 and the second cover taperportion 320 define a conical shape. FIG. 13 is a side perspective viewof another balloon cover 1300, in accordance with an embodiment. Theballoon cover 1300 is substantially similar to the embodiment as shownin FIG. 8A, but for comprising a first cover taper portion 1324 and asecond cover taper portion 1324 defining a spherical shape.

In various alternate balloon configurations, the balloon and ballooncovers in accordance with embodiments provided herein may incorporateadditional cover layers that can alter the properties of the balloon orof the balloon system. In particular, additional balloon covers canalter the balloon shape as the balloon is inflated. Other additionalcovers, in accordance with embodiments, can alter or enhance theinflation profiles of a balloon. In addition, cover leg portions may beprovided to the balloon cover that is complementary to the balloon legportions 204, as shown in FIG. 3A, to allow the high-strength bonding ofthe balloon covers to the balloon. In one embodiment, the additionalballoon covers comprise a frangible balloon cover. In anotherembodiment, the frangible balloon cover comprises ePTFE.

EXAMPLES

Without intending to limit the scope of the invention, the followingexamples illustrate how various embodiments of the invention may be madeand/or used

Example 1

A balloon cover in accordance with an embodiment was fabricatedaccording to the previously described methods, with the followingadditional details:

A mandrel was provided that had the following dimensions: firstcylindrical portion diameter was 1.142″, first cylindrical portionlength was 1.378″, second cylindrical portion diameter was 1.130″,second cylindrical portion length was 1.378″, the opposing taperportions had 90° included angles and the opposing shafts had diametersof 0.157″. The mandrel was fabricated from 300 series stainless steel.

The manufacturing aid (film) was about 0.75 wide and about 8″ long. Thefilm strap comprised a densified fluoropolymer as described in U.S. Pat.No. 7,521,010 to Kennedy et al., laminated with a fluoroelastomerthermoplastic adhesive, as described in U.S. Pat. No. 7,462,675 to Changet al. The film had the following properties:

-   -   Composite thickness=5 μm    -   Composite mass per area=11.1 g/m2    -   Machine Direction Matrix Tensile Strength=356 MPa.

Three full circumferential wraps were layered onto the mandrel. Theheat-tacking soldering iron was set to about 650° F.

The film straps were about 0.75″ wide and were of the same film as themanufacturing aid described above. The circumferential wrapped film wasabout 1″ wide and was of the same film as the manufacturing aiddescribed above.

The heat treat temperature was about 250° C. and the heat treatment timewas about 30 minutes.

The first and second cover portions were cut to have cover body portionsof about 25 mm.

The metallic ring had a length of about 24 mm, an outer diameter ofabout 38 mm, an inner diameter of about 35 mm and was fabricated from300 series stainless steel. The high temperature polymeric film was0.004″ thick, 40 mm wide Kapton®. The high temperature fiber was a heatshrinkable fluoropolymer. The heat treat temperature was about 250° C.and the heat treatment time was about 30 minutes.

The balloon was fabricated from Polyethylene Terephthalate (PET,Thermoplastic Polyester) and had a nominal outer diameter of about 29mm, a nominal working length of about 26 mm, a nominal wall thickness(along the working length) of about 0.0028″, included cone angles ofabout 90° and opposing leg portion outer diameters of about 3.4 mm. Theballoon cover was slidingly engaged over the balloon and was bonded tothe underlying balloon with LOCTITE® adhesive part number 495 and wasthen ambient cured.

The balloon cover was undersized, relative to the balloon inflateddiameter, by about 5%, allowing the balloon cover to absorb the loadimparted to the cover by the inflated balloon.

Example 2

The balloon with attached balloon covers from Example 1 was subjected toa pull through test. The pull through test was designed to measure theforce required to pull a deflated balloon through a series of gageholes. The test was designed to emulate the force required to retract adeflated balloon back into an introducer sheath.

A vertical universal mechanical testing system (Instron®, Model 5564,Norwood, Mass., USA) with a 10.2 kg tension load cell was configured tomeasure pull through forces. A water bath was aligned to the testingsystem and heated to about 37° C. A longitudinally split gage, having aseries of varying diameter pull through holes was fixed within theheated water bath.

A balloon catheter with an attached balloon cover from Example 1 wasprovided. A distal portion of the balloon catheter shaft was clamped tothe load cell head. The gage with a series of varying diameter pullthrough holes was “split open” to allow a proximal portion of thecatheter shaft to be inserted into a first, large diameter hole (22 F orabout 0.29″ with a chamfered/broken edge lead in). The gage halves werethen aligned and clamped together, surrounding the proximal portion ofthe catheter shaft. The balloon was then inflated to about 2 atm andthen deflated with a vacuum. The vacuum was maintained with a stopcocklocated on the proximal end of the catheter. The deflated balloon withballoon cover was then pulled up through the gage hole at rate of about10″/minute while the instant pull force was recorded.

The gage was then opened and the catheter shaft was positioned into thenext smaller gage hole. The gage was reassembled, the balloon wasre-inflated to about 2 atm and deflated as previously described. Thedeflated balloon with balloon cover was then pulled through the gagehole while the instant pull force was recorded.

The test sequence was repeated using progressively smaller gage pullthrough holes. The test sequence was terminated if the balloon rupturedor leaked during inflation, or if the pull force exceeded apre-determined limit. The pull through hole diameters for a typical 29mm underlying balloon with balloon cover according to Example 1 rangedfrom 22 F (about 0.29″) to 11 F (about 0.145″).

Balloons without a balloon cover in accordance with embodiments providedherein were also evaluated on the pull through test to generatecomparative data.

Example 3

A balloon with attached balloon cover from Example 1 was subjected to aballoon compliance, inflation/burst test. The balloon compliance,inflation/burst test was designed to measure the balloon diameter vs.internal pressure along with determining the internal balloon pressurerequired to rupture/burst the balloon with attached balloon cover fromExample 1.

A balloon compliance/burst test system was provided (InterfaceAssociates, Laguna Niguel, Calif., USA, Model PT3070). The test systemhad a water bath heated to about 37° C., a pressurized waterfeed/pressure measurement system, and a laser micrometer to measure theouter diameter of the expanded balloon and balloon cover. The ballooncompliance/burst test parameters are displayed in TABLE 1 below:

TABLE 1 Test Parameter Setting Pressurization Ramp Rate (ml/s) 1.0Pressurization Alarm Drop 2.50 Pressurization Time* (sec) PressurizationMax Pressure (atm) 50.00 Pressurization Max Volume (ml) 200.00Pressurization Max Diameter (mm) 55.00 Start Up Position 0.10 Start UpVacuum Pressure −0.50 Pressure Units atm Diameter Units mm Ramp TargetOffset Pressure (atm) 0.00 Pre-Fill Volume (ml) 20.00 Pre-Fill Pressure(atm) 1.00 Pre-Fill Rate (ml/s) 0.50

The balloon with attached balloon cover was purged of air by a series ofvacuum air withdrawals followed by water inflations. The purging wasrepeated until no more air could be withdrawn from the balloon catheter.After air purging, the catheter was subjected to the compliance/bursttest.

Balloons without the balloon cover in accordance with embodimentsprovided herein were also evaluated on the compliance/burst test togenerate comparative data.

Example 4

Balloons with attached cover from Example 1 were subjected to the pullthrough test (Example 2) and to the balloon compliance, inflation/bursttest (Example 3). Additionally, balloons without a balloon cover weresubjected to the pull through and compliance/burst test to generatecomparative data. The test results are displayed in FIGS. 11A and 11B.

These data show that the presence of a balloon cover in accordance withembodiments provided herein significantly raises the burst strength ofthe balloon with balloon cover system without significantly compromisingthe pull through force.

Balloon covers in accordance with embodiments provided herein increasesthe strength of a balloon to attain a higher rated burst pressure whilemaintaining a low delivery profile. Further, balloon covers inaccordance with embodiments provided herein control the profile of theballoon during inflation providing a consistent and uniform diameteralong the working length of the balloon.

Balloon covers may prevent one end of the balloon from attaining anexpanded diameter prior to the opposing end, or the middle of theballoon prior to the ends. This consistency of profile during inflationdecreases the likelihood that a stent will be dislodged longitudinallyalong the length of the balloon moving either partially or fully off theballoon. The consistency of profile during inflation decreases thelikelihood for vessel trauma as a stent is evenly expanded andsubsequently evenly engages a vessel wall.

In accordance with another embodiment, a balloon cover is provided thatis operable to provide one or more intermediate inflated diameters thatare apparent to a doctor during delivery that provides a uniform profile(that is, a relatively uniform diameter) along the length of the balloonat each intermediate diameter. In accordance with an embodiment, aballoon cover is provided that is operable such that the balloon mayinflate to an intermediate diameter at a first pressure and a seconddiameter larger than the intermediate diameter at a second pressure.

In accordance with another embodiment, a balloon cover is provided thatis operable to provide one or more intermediate inflated diameters thatare apparent to a doctor during delivery that provides a uniform profile(that is, a relatively uniform diameter) along the length of the balloonat each intermediate diameter, wherein the balloon is non-compliant.Non-compliant as defined herein is a characteristic of a balloon that,by itself, inflates to a preset diameter even as pressure is increased.Compared with a balloon comprising a material that may stretch underincreasing pressure which is therefore considered to be compliant. Inaccordance with an embodiment, a balloon cover is provided that isoperable such that the balloon may inflate to an intermediate diameterat a first pressure and a second diameter larger than the intermediatediameter at a second pressure.

FIG. 15A is a balloon diameter vs. balloon pressure graph, generallydepicting an inflation sequence 1700 a of a balloon cover systemcomprising means operable to provide an intermediate and final inflateddiameter that is apparent to a doctor during delivery that provides auniform profile (that is, a relatively uniform diameter) along thelength of the balloon at each intermediate and final diameters. Theballoon has an initial diameter in an un-inflated state of about 4 mm(1702). As pressure increases in the balloon, the balloon diameterincreases (1704) to an intermediate diameter of about 14 mm while thepressure increases to about 5 atm (1708). At about 5 atm with theballoon at an approximate 14 mm diameter, the means operable to providean intermediate and final inflated diameter allows the balloon tocontinue to expand (1710) while at an approximate pressure of 2 atm(1712). At a diameter of about 23 mm, the balloon and balloon coverresist further expansion and the pressure begins to rise (1714). As thepressure increases above 2 atm the balloon remains at essentially 25 mm(1716) which may be the final diameter that is desired for theparticular purpose.

The relatively more rapid increase in pressure between about 2 atm and 5atm at (1708) may provide for the balloon to establish a uniform profile(diameter) along the length of the balloon. For example, but not limitedthereto, any folds, wrinkles or other uneven inflation profile of theballoon along the length of the balloon caused by being compressed ontothe catheter shaft have been smoothed out under the inflation pressureat (1708). The increase in pressure at (1708) provides the doctortactile feedback that the balloon has expanded to about the intermediatediameter. The rapid drop in pressure at (1711) provides the doctortactile feedback that the balloon has been released to allow furtherexpansion. The increase in diameter at a relatively uniform pressure at(1712) provides that the balloon may expand while retaining a uniformprofile (diameter) along the length of the balloon. The increase inpressure at (1714) provides the doctor tactile feedback that the balloonhas expanded to about the final diameter.

FIG. 15B is a balloon diameter vs. balloon pressure graph generallydepicting an inflation sequence 1700 b of a balloon cover systemcomprising means operable to provide multiple intermediate diameters anda final inflated diameter that is apparent to a doctor during deliverythat provides a uniform profile (that is, a relatively uniform diameter)along the length of the balloon at each intermediate and finaldiameters. The balloon has an initial diameter in an un-inflated stateof about 4 mm (1702). As pressure increases in the balloon, the balloondiameter increases (1704) to a first intermediate diameter of about 14mm (1710 a) while the pressure increases to about 5 atm. At about 5 atmwith the balloon at an approximate 14 mm diameter, the means operable toprovide multiple intermediate and final inflated diameters allows theballoon to continue to expand (1710 a) while at an approximate pressureof 2 atm (1712 a). As the pressure increases to above 2 atm (1714 a),the balloon remains at approximately 23 mm (1710 b). At about 7 atm withthe balloon at an approximate 23 mm diameter, the means operable toprovide multiple intermediate and final inflated diameters allows theballoon to continue to expand (1710 b) while at an approximate pressureof 4 atm. At a second intermediate diameter of about 26 mm, the balloonand balloon cover resist further expansion (1714 b). As the pressureincreases to above 4 atm, the balloon remains at approximately 26 mm(1716) which may be the final diameter that is desired for theparticular purpose.

The relatively more rapid increase in pressure between about 2 atm and 5atm at (1708) may provide for the balloon to establish a uniform profile(diameter) along the length of the balloon. For example, but not limitedthereto, any folds, wrinkles or other uneven inflation profile of theballoon along the length of the balloon caused by being compressed ontothe catheter shaft have been smoothed out under the inflation pressureat (1708). The increase in pressure at (1708) provides the doctortactile feedback that the balloon has expanded to about the firstintermediate diameter. The rapid drop in pressure at (1711 a) providesthe doctor tactile feedback that the balloon has been released to allowfurther expansion. The increase in diameter at a relatively uniformpressure at (1712) provides that the balloon may expand while retaininga uniform profile (diameter) along the length of the balloon. Theincrease in pressure at (1714 a) provides the doctor tactile feedbackthat the balloon has expanded to about the second intermediate diameter.The rapid drop in pressure at (1711 b) provides the doctor tactilefeedback that the balloon has been released to allow further expansion.The increase in pressure at (1714 b) provides the doctor tactilefeedback that the balloon has expanded to about the final diameter.

The compliance (pressure vs. diameter) curve as provided in accordancewith the embodiments of FIGS. 15A and 15B with various points along thecurve is operable to deliver a stent that is on the balloon in a uniformprofile along the length of the stent in a predictable manner at anintermediate diameter. Further, an inflation profile as provided inaccordance with the embodiments of FIGS. 15A and 15B is operable todeliver a stent that is on the balloon with a uniform profile along thelength of the stent with increasing diameter that provides the doctorwith a safe, customizable intermediate diameter for which to deliver thestent.

In accordance with an embodiment, means operable to provide anintermediate and final inflated diameter to a balloon that is apparentto a doctor during delivery that provides a uniform profile (that is, arelatively uniform diameter) along the length of the balloon at eachintermediate and final diameters comprises a frangible balloon coveroperable to allow the balloon to inflate to a predetermined diameterwhile allowing the balloon to have a substantially uniform diameteralong the working length of the balloon. Then, as pressure increaseswithin the balloon that is inflated from a single inflation lumen, thefrangible balloon cover ruptures allowing the balloon to increase to apredetermined diameter. In an embodiment, the balloon increases indiameter evenly along the working length of the balloon.

In an embodiment, an external constraint allows the balloon to open to apredetermined intermediate diameter that is less than the fully expandedworking diameter of the balloon. An external constraint is any elementthat resides outside of the balloon. The external constraint allows theballoon to have a substantially uniform diameter long the working lengthof the balloon. As pressure increases within the balloon that isinflated from a single inflation lumen, the external constraint releasesthe balloon at a predetermined pressure allowing the balloon to increasein diameter. In an embodiment, the balloon increases in diametersubstantially uniformly along the working length of the balloon. Inaccordance with embodiments, the external constraint is a frangiblecover.

In accordance with an embodiment, the external constraint allows theballoon to open to a predetermined intermediate diameter that is greaterthan about 20% than the fully expanded working diameter of the balloon.In accordance with another embodiment, the external constraint allowsthe balloon to open to a predetermined intermediate diameter that isgreater than about 30% than the fully expanded working diameter of theballoon. In accordance with another embodiment, the external constraintallows the balloon to open to a predetermined intermediate diameter thatis greater than about 50% than the fully expanded working diameter ofthe balloon.

In an embodiment, a frangible balloon cover allows the balloon to opento a predetermined diameter that is less than the fully expanded workingdiameter of the balloon. The various covers incorporated onto balloonsin accordance with embodiments provided herein allow the balloon to havea substantially uniform diameter long the working length of the balloon.As pressure increases within the balloon that is inflated from a singleinflation lumen, the frangible cover breaks, allowing the balloon toincrease in diameter. In an embodiment, the balloon increases indiameter substantially uniformly along the working length of theballoon.

In another embodiment, a frangible balloon cover allows the balloon toopen to a predetermined diameter that is less than the fully expandedworking diameter of the balloon as well as elongate to a longer workinglength. FIG. 17D is a side cross-sectional view of a frangible balloonassembly 1600 b showing the catheter shaft 104, the balloon 200, thefrangible cover 1650 and the outer cover 1616 in a state of intermediateinflation wherein the frangible cover 1650 is not ruptured and thediameter of the frangible balloon assembly 1600 b is at an intermediatediameter Di and the length of the balloon L1 is smaller than the balloonworking length Lw, in accordance with an embodiment. FIG. 17E is a sidecross-sectional view of a frangible balloon assembly 1600 b showing thecatheter shaft 104, the balloon 200, the frangible cover 1650 and theouter cover 1616 in a state of inflation to the balloon working diameterwherein the frangible cover 1650 has ruptured releasing the balloon 200to attain a final diameter Df and to the working length Lw, inaccordance with an embodiment. The various covers incorporated ontoballoons in accordance with embodiments provided herein allow theballoon to have a substantially uniform diameter along the workinglength of the balloon. As pressure increases within the balloon that isinflated from a single inflation lumen, the frangible cover breaks,allowing the balloon to increase in diameter and length. In anembodiment, the balloon increases in diameter substantially uniformlyalong the working length of the balloon.

In another embodiment, a stent may be placed adjacent to the frangiblecover, the stent may be put directly on the frangible cover or there canbe another layer on top of the frangible cover. Thus, as the balloonincreases in diameter, a stent also increases in diameter to apredetermined diameter controlled by the frangible cover. At this stagethe stent may have substantially the same diameter along the length ofthe stent. After the frangible cover breaks, the balloon and stentincrease in diameter evenly along the working length of the balloon andalong the length of the stent.

FIG. 16A is a side cross-sectional view of a frangible balloon assembly1600 a including a catheter shaft 104, a balloon 200, and a frangibleballoon cover 1645 comprising a legged balloon cover 300 b and afrangible cover 1650, in accordance with an embodiment. Shown are thecatheter shaft 104, an inflation lumen 105, and inflation ports 125 withthe attached balloon 200. The balloon may be inflated from the singleinflation lumen. The balloon 200 comprises balloon leg portions 204 (asalso shown in FIG. 2). The balloon 200 is shown in FIG. 16A beinginflated to an intermediate diameter prior to the rupturing of thefrangible cover 1650. The intermediate diameter is smaller than aworking diameter of the balloon 200. A working diameter of the balloonis defined as the maximum diameter of the inflated balloon. Thefrangible balloon cover 1645 is positioned around balloon taper portions206 and a balloon body portion 208 of the balloon 200.

Referring again to FIGS. 8B and 16A, the legged balloon cover 300 bcomprises a first legged cover portion 313 b and a second legged coverportion 315 b. The first legged cover portion 313 b includes a firstcover body portion 312 integrally connected to a first cover taperportion 314, further comprising a cover leg portion 1504 located at anapex of the first cover taper portion 314. The second legged coverportion 315 b includes a second cover body portion 318 integrallyconnected to a second cover taper portion 320, further comprising acover leg portion 1504 located at an apex of the second cover taperportion 320.

The first cover body portion 312 is operable to overlay a portion of theballoon body portion 208. The first cover taper portion 314 is operableto overlay a portion of the balloon taper portion 206. The cover legportion 1504 is operable to allow the balloon leg portion 204 of theballoon 200 to pass through.

The second cover body portion 318 is operable to overlay a portion ofthe balloon body portion 208. The second cover taper portion 320 isoperable to overlay a portion of the balloon taper portion 206. Thecover leg portion 1504 is operable to allow the balloon leg portion 204of the balloon 200 to pass through.

Referring again to FIG. 16A, the first cover taper portion 314 and thesecond cover taper portion 320 are located at opposite ends of theballoon cover 300 b. The first cover portion 313 and the second coverportion 315 are coaxially aligned along axis X and overlay the balloon200 such that at least a portion of the first cover body portion 312overlays at least a portion of the second cover body portion 318.

FIG. 17A is a side view of the frangible cover 1650 in accordance withan embodiment. As shown in FIG. 16A, the frangible cover 1650 overlaysthe first cover body portion 312, the second cover body portion 318, andat least a portion of each of the first cover taper portion 314 and thesecond cover taper portion 320. The frangible cover 1650 is operable tocontrol the inflation of the balloon 200 to a first intermediatediameter that is larger than the pre-inflated diameter of the balloon200. When the internal pressure of the balloon 200 reaches a firstpredetermined pressure the frangible cover 1650 is operable to rupturepermitting the balloon 200 to inflate to the working diameter of theballoon 200 which is larger than the first intermediate diameter (seeFIGS. 17B and 17C).

Rupturing as defined herein is to brake, tear, distort or yield, and, asused with regard to the frangible cover, rupturing of the frangiblecover is operable to release the balloon from a constrained diameterallowing the underlying balloon to expand to a larger diameter.

In accordance with an embodiment, the balloon cover assembly 1600 afurther comprises an optional outer cover 1616 that covers the frangiblecover 1650 and first cover leg portion 1504 and second cover leg portion1504. The outer cover 1616 has a form substantially similar to theballoon as shown in FIG. 2. The outer cover 1616 may be coupled to thefirst cover leg portion 1504 and second cover leg portion 1504. Theouter cover 1616 is operable to contain any fragments or loose edges ofthe frangible cover 1650 that may form as a result of the frangiblecover rupturing. The optional outer cover 1616 may also be operable toprevent a stent placed thereon from sliding along the length of theballoon cover.

FIG. 16B is a side cross-sectional view of a frangible balloon assembly1600 b including a catheter shaft 104, a balloon 200, and a frangiblecover 1650, in accordance with an embodiment. Shown are the cathetershaft 104, an inflation lumen 105 and inflation ports 125 with theattached balloon 200. The balloon may be inflated from the singleinflation lumen. The balloon 200 comprises balloon leg portions 204 (asalso shown in FIG. 2). The balloon 200 is shown in FIG. 16B beinginflated to an intermediate diameter prior to the rupturing of thefrangible cover 1650. The intermediate diameter is smaller than aworking diameter of the balloon 200. A working diameter of the balloonis defined as the maximum diameter of the inflated balloon. Thefrangible balloon cover 1645 is positioned around balloon taper portions206 and a balloon body portion 208 of the balloon 200.

FIG. 17A is a side view of the frangible cover 1650 in accordance withan embodiment. As shown in FIG. 16B, the frangible cover 1650 overlaysthe balloon body portion 208 and at least a portion of each of theballoon taper portions 206. The frangible cover 1650 is operable tocontrol the inflation of the balloon 200 to a first intermediatediameter that is larger than the pre-inflated diameter of the balloon200. When the internal pressure of the balloon 200 reaches a firstpredetermined pressure the frangible cover 1650 is operable to rupturepermitting the balloon 200 to inflate to the working diameter of theballoon 200 which is larger than the first intermediate diameter.

FIG. 17B is a side cross-sectional view of a frangible balloon assembly1600 b showing the catheter shaft 104, the balloon 200, the frangiblecover 1650 and the outer cover 1616 in a state of intermediate inflationwherein the frangible cover 1650 is not ruptured and the diameter of thefrangible balloon assembly 1600 b is at an intermediate diameter Di, inaccordance with an embodiment. FIG. 17C is a side cross-sectional viewof a frangible balloon assembly 1600 b showing the catheter shaft 104,the balloon 200, the frangible cover 1650 and the outer cover 1616 in astate of inflation to the balloon working diameter wherein the frangiblecover 1650 has ruptured releasing the balloon 200 to attain a finaldiameter Df, in accordance with an embodiment.

Rupturing as defined herein is to brake, tear, distort or yield, and, asused with regard to the frangible cover, rupturing of the frangiblecover is operable to release the balloon from a constrained diameterallowing the underlying balloon to expand to a larger diameter.

In accordance with an embodiment, the balloon cover assembly 1600 bfurther comprises an optional outer cover 1616 that covers the frangiblecover 1650 and first balloon leg portion 204 and second balloon legportion 204. The outer cover 1616 has a form substantially similar tothe balloon as shown in FIG. 2. The outer cover 1616 may be coupled tothe first balloon leg portion 204 and second balloon leg portion 204.The outer cover 1616 is operable to contain any fragments or loose edgesof the frangible cover 1650 that may form as a result of the frangiblecover rupturing. The optional outer cover 1616 may also be operable toprevent a stent placed thereon from sliding along the length of theballoon cover.

FIG. 16C is a side cross-sectional view of a frangible balloon assembly1600 c including a catheter shaft 104, a balloon 200, and a firstfrangible cover 1650 a, a second frangible cover 1650 b, and a thirdfrangible cover 1650 c, in accordance with an embodiment. Shown are thecatheter shaft 104, an inflation lumen 105, and inflation ports 125 withthe attached balloon 200. The balloon may be inflated from the singleinflation lumen. The balloon 200 comprises balloon leg portions 204 asshown in FIG. 2. The balloon 200 is shown in FIG. 16C being inflated toa first intermediate diameter prior to the rupturing of the firstfrangible cover 1650 a. The first frangible cover 1650 a, secondfrangible cover 1650 b, and third frangible cover 1650 c are positionedsequentially around a balloon body portion 208 of the balloon 200. Inother embodiments the first frangible cover 1650 a, second frangiblecover 1650 b, and third frangible cover 1650 c may extend over theballoon taper portions 206 and the balloon body portion 208 of theballoon 200.

The first intermediate diameter is smaller than the second intermediatediameter that is smaller than a third intermediate diameter which issmaller than a working diameter of the balloon 200. A working diameterof the balloon is defined as the maximum diameter of the inflatedballoon. The frangible balloon cover 1645 is positioned around balloontaper portions 206 and a balloon body portion 208 of the balloon 200.

The first frangible cover 1650 a is operable to control the inflation ofthe balloon 200 to a first intermediate diameter that is larger than thepre-inflated diameter of the balloon 200. When the internal pressure ofthe balloon 200 reaches a first predetermined pressure the firstfrangible cover 1650 a is operable to rupture permitting the balloon 200to inflate to a second intermediate diameter larger than the firstintermediate diameter (See FIGS. 17B and 17C).

Rupturing as defined herein is to brake, tear, distort or yield, and, asused with regard to the frangible cover, rupturing of the frangiblecover is operable to release the balloon from a constrained diameterallowing the underlying balloon to expand to a larger diameter.

The second frangible cover 1650 b is operable to control the inflationof the balloon 200 to a second intermediate diameter that is larger thanthe first intermediate diameter. When the internal pressure of theballoon 200 reaches a second predetermined pressure the second frangiblecover 1650 b is operable to rupture permitting the balloon 200 toinflate to a third intermediate diameter larger than the secondintermediate diameter.

The third frangible cover 1650 c is operable to control the inflation ofthe balloon 200 to a third intermediate diameter that is larger than thesecond intermediate diameter. When the internal pressure of the balloon200 reaches a third predetermined pressure the third frangible cover1650 c is operable to rupture permitting the balloon 200 to inflate tothe working diameter of the balloon 200 which is larger than the thirdintermediate diameter.

The first frangible cover 1650 a, second frangible cover 1650 b, andthird frangible cover 1650 c are shown in FIG. 16C having increasingthickness, respectively, as an example of imparting material strength tothe frangible covers such that they rupture at increasingly higherpressures, respectively. It is understood and appreciated that ruptureof the frangible cover at predetermined pressures may be affected bymany means, including, but not limited to, material physical properties.

In accordance with an embodiment, the balloon cover assembly 1600 cfurther comprises an optional outer cover 1616 that covers the firstfrangible cover 1650 a, second frangible cover 1650 b, and thirdfrangible cover 1650 c and balloon leg portions 204. The outer cover1616 has a form substantially similar to the balloon as shown in FIG. 2.The outer cover 1616 may be coupled to the balloon leg portions 204. Theouter cover 1616 is operable to contain any fragments or loose edges ofthe first frangible cover 1650 a, second frangible cover 1650 b, andthird frangible cover 1650 c that may form as a result of the frangiblecovers rupturing. The optional outer cover 1616 may also be operable toprevent a stent placed thereon from sliding along the length of theballoon cover.

In accordance with embodiments, the frangible cover is made of amaterial that has a very predictable elongation to break. In accordancewith an embodiment, this elongation to break is very abrupt leading tocomplete failure with tear propagation allowing the frangible cover tofail in entirety. In accordance with an embodiment, a material has anelongation to break of <30%, or <20%, or preferably <15%. In accordancewith an embodiment, the frangible cover is operable to have anelongation to fail that is approximately less than 15% of itsmanufactured diameter. That is to say, a frangible cover fabricated to a14 mm diameter will provide an intermediate diameter that predictablywill rupture at approximately 16 mm.

In accordance with an embodiment, a frangible cover comprises elementsto allow the propagation of a tear completely across the frangiblecover. FIG. 18A is a frangible cover 1650 d comprising elongated nodes1802 of ePTFE that are substantially oriented along a longitudinal axisof the frangible cover 1650 d, or perpendicular to the applied hoopstress, in accordance with an embodiment. Such orientation allows forlongitudinal tearing of the frangible cover 1650 d at locations betweenthe elongated nodes 1802.

In an alternate embodiment, the frangible cover comprises a materialwith a yield point followed by a high degree of lower load plasticdeformation. For example, a frangible cover is operable to provide anintermediate inflation diameter of, by way of example, 14 mm-16 mm andoperable to immediately yield upon distention, followed by at least 80%elongation at a lower load plateau to a final balloon diameter of 25 mm.

In an alternate embodiment, the frangible cover comprises an elementthat is operable to cause abrupt failure of the frangible cover at apredictable load. In accordance with embodiments, this element includes,but not limited to, notches 1806 as provided in frangible cover 1650 eas shown in FIG. 18B, perforations 1808 as provided in frangible cover1650 f as shown in FIG. 18C, holes, and densifications. In accordancewith embodiments, this feature includes a seam, a joint 1810 as shown inFIG. 18D, or other means of holding the frangible cover in a tubularform until a predictable amount of load is applied.

In accordance with embodiments, additional frangible covers can beprovided operable to cause multiple “spikes” similar to 1710 along theplateau 1712. The multiple frangible release layers can be tailored tosplit at specific diameters, such as at 20 mm, 25 mm etc.

FIG. 19A is a stress-strain curve depicting a profile of a materialproperty that would enable a frangible cover to control a balloon to anintermediate diameter then rupture. FIG. 19B is a stress-strain curvedepicting a profile of a material property that would enable a frangiblecover to control a balloon to an intermediate diameter then yield.

Example 5

The following describes an embodiment of a method utilizing thin,polymeric film lay-ups used to fabricate balloon covers in accordancewith embodiments provided herein. This configuration is constructed ingeneral accordance with the previously described methods and Example 1.This embodiment of the method includes the addition of balloon cover legportions, the addition of a frangible cover along with the addition ofan outer cover. This method can comprise the following steps:

Cover leg portions 1504, shown in FIG. 8B, were added to the first coverportion 313 and to the second cover portion 315.

An assembly as shown in FIG. 14 was provided. The assembly 1406comprises a mandrel 1400, a wrapped manufacturing aid 1402 and threepolymeric film straps 1404. The assembly 1406 was formed using thematerials and process as previously described in Example 1.

As shown in FIG. 14B, a cover leg portion 1408 was added to the assembly1406. A thin-walled, radially expandable ePTFE tube 1410 was stretchedover the mandrel shaft 1412 and partially up onto the mandrel taperportion 1414. The tube 1410 partially covered the three polymeric filmstraps 1404. The thin-walled ePTFE tube 1410 had an initial diameter ofabout 4 mm and a length of about 50 mm. The excess length of the tubing1410 was trimmed to expose about 10 mm of the mandrel shaft 1412.

A circumferential film wrap was then added according to previouslydescribed Example 1. Three additional film straps were then addedaccording to previously described Example 1. The three additional filmstraps covered the taper portion 1416 of the thin-walled, radiallyexpandable ePTFE tube 1410.

Similarly, a cover leg portion 1408 was then added to the opposingmandrel end following previously described assembly in Example 1,resulting in a pair of balloon covers as shown in FIG. 8B. As shown inFIG. 8B, a first cover body portion 312 haves a first cover body portion312 having a working length 802 integrally connected to a first covertaper portion 314. The first cover taper portion 314 has a cover legportion 1504 located at an apex of the first cover taper portion 314.Also shown in FIG. 8B is a second cover portion 315 having a secondcover body portion 318 having a working length 1512 integrally connectedto a second cover taper portion 320. The second cover taper portion 320has a cover leg portion 1504 located at an apex of the second covertaper portion 320.

As further shown in FIG. 8B, the second cover portion 315 can beinserted into the first cover portion 313 by translating the second bodyportion 318 into the first cover body portion 312 as indicated bydirection arrows (820, 822), so that the first cover body portion 312and the second body portion 318 are substantially overlapped (aspreviously defined).

The first cover body portion 312 and the second body portion 318 werethen bonded together along the working lengths according to Example 1.

A compacted and folded PET balloon was then inserted into the bondedfirst cover body portion 312 and second cover portion 315 according toprevious Example 1. In this embodiment the cover leg portions 1504 werebonded to the underlying balloon leg portions 204. No adhesive wasinjected between the first and second cover body portions and theballoon body portion. To bond the first and second cover leg portions tothe balloon leg portions, an ePTFE film was imbibed with an adhesive andthe film was then wrapped around the balloon leg portions. The ePTFEfilm had a high degree of longitudinal strength, was about 6 mm wide andwas imbibed with LOCTITE® 4981 adhesive. Hand tension was applied to thefilm as the film was wrapped around the balloon leg portions. Fivelayers of film were applied.

A frangible cover was then applied to the balloon cover. An ePTFE filmtube was formed by longitudinally wrapping nine layers of a 90 mm widefilm onto a 14 mm mandrel. The film had an elongation to break ofapproximately 12% (7%-17%), and a maximum tensile load of roughly 1.2(0.7 to 1.7) pounds per linear inch. The longitudinally wrapping is alsoreferred to as a “cigarette” wrap. The precursor material and film aredescribed in U.S. Pat. No. 5,708,044 to Branca and in U.S. Pat. No.5,814,405 to Branca et al., both of which are incorporated by referenceherein in their entirety. The film was oriented such that its fibrilswere aligned with the circumference, which provides a high degree ofresistance to elongation during inflation allowing the balloon to buildpressure until that of about 5 atm. The film was oriented such that itslong nodes were oriented perpendicular to the circumference providing ameans for complete tear propagation along the length of the frangiblecover when the frangible cover is taken past its maximum inflationpressure or to a diameter past that of approximately 16 mm. Thefrangible cover was then positioned over the balloon cover. Thefrangible cover had a length that approximated the overall balloonlength, minus the lengths of the balloon leg portions as shown in FIG.16A. The radial force required to split the frangible cover can be setby varying the number of layers of a given frangible film that comprisesthe frangible cover.

An outer cover was then added to cover the frangible cover. The outercover was fabricated by the following process:

An ePTFE film was helically wrapped around a mandrel having a diameterof about 25 mm and a length of about 37 cm. The film width was about2.54 cm. Twenty layers were wrapped in a helical pattern having a 1.85°pitch angle. The wrapped length was about 30 cm.

The film wrapped mandrel was then placed into an air convection ovenheated to about 380° C. for about 25 minutes. This heat exposure bondedthe layers of ePTFE, forming a thin film tube.

The ePTFE film wrapped mandrel was removed from the oven, allowed tocool, and the thin film tube was removed from the mandrel. The thin filmtube had a diameter of about 25 mm and a wall thickness of about 0.0254mm.

The about 30 cm long thin film tube was then tensioned by hand andstretched longitudinally to about 400% of the original length, or toabout 120 cm. After stretching, the tube was placed onto a mandrelhaving a diameter of about 4 mm and a length of about 130 cm. Thestretched tube was smoothed by hand onto the mandrel, forming a smalldiameter thin film tube having a diameter of about 4 mm.

A temporary ePTFE film was then helically wrapped onto the about 4 mmdiameter thin wall tube. The film thickness was about 0.00508 mm and thefilm width was about 1.905 cm. One pass of film was wrapped, using a2.6924 mm pitch (measured from adjacent film edges) with a film angle ofabout 78°.

The thin film tube and temporary ePTFE film wrap was then longitudinallycompressed by 40%, from a starting length of about 130 cm to acompressed length of about 78 cm.

The longitudinally compressed thin film tube and mandrel was then placedinto an air convection oven heated to about 380° C. for about 1 minute.

The ePTFE film wrapped mandrel was then removed from the oven andallowed to cool.

The temporary ePTFE film wrap was then removed from the thin film tube.

The outer cover was then positioned onto the frangible cover. The outercover had a length that approximated the overall balloon length as shownin FIG. 16A. The ends of the outer cover were aligned to the ends of theballoon leg portions.

The outer cover was then bonded to the underlying frangible cover usingan ePTFE film imbibed with an adhesive. The imbibed film was wrappedaround the underlying balloon cover leg portions. The ePTFE film had ahigh degree of longitudinal strength, was about 6 mm wide and wasimbibed with LOCTITE® 4981 adhesive. Hand tension was applied to thefilm as five layers of film were applied.

The resulting covered balloon had a cross-section as shown in FIG. 16Aand as previously described. A PET balloon 200 is bonded to the cathetershaft 104 with an adhesive 1608 along the balloon leg portions 204. Afirst cover portion 313 and a second cover portion 315 are showncovering the PET balloon 200. The first cover portion 313 and a secondcover portion 315 are joined along a bond line 1610. The cover legportions of the first cover portion 313 and a second cover portion 315are bonded to the PET balloon 200 by an adhesive imbibed film 1612. Thefrangible cover 1650 is shown surrounding the first cover portion 313and a second cover portion 315. An outer cover 1616 is shown coveringthe frangible cover 1650. The outer cover 1616 is shown bonded to thecover leg portions by an adhesive imbibed film 1618.

Testing of the device of Example 5 provided a balloon diameter vs.pressure profile substantially as shown in FIG. 15A, generally depictingan inflation sequence 1700 of the balloon described in FIG. 16. Theballoon had an initial diameter of about 4 mm indicated as 1702. Aspressure was applied to the balloon, the balloon began to expand. Theballoon diameter increased as the frangible cover began to resistfurther expansion when the balloon diameter reached about 14 mm (1708).The frangible cover split (1710) at about 5 atm while at an approximate14 mm diameter. The balloon then continued to expand in diameter (1712)while at an approximate pressure of 2 Atm. At a diameter of about 25 mm,the first cover portion 313 and a second cover portion 315 began toresist further expansion (1714). As the pressure was increased to above2 atm, the balloon remained at essentially 25 mm (1716). At a pressureof about 10 atm, the balloon burst (1718).

Numerous characteristics and advantages of the present invention havebeen set forth in the preceding description, including preferred andalternate embodiments together with details of the structure andfunction of the invention. The disclosure is intended as illustrativeonly and as such is not intended to be exhaustive. It will be evident tothose skilled in the art that various modifications may be made,especially in matters of structure, materials, elements, components,shape, size and arrangement of parts within the principals of theinvention, to the full extent indicated by the broad, general meaning ofthe terms in which the appended claims are expressed. To the extent thatthese various modifications do not depart from the spirit and scope ofthe appended claims, they are intended to be encompassed therein. Inaddition to being directed to the embodiments described above andclaimed below, the present invention is further directed to embodimentshaving different combinations of the features described above andclaimed below. As such, the invention is also directed to otherembodiments having any other possible combination of the dependentfeatures claimed below.

What is claimed is:
 1. A catheter balloon assembly comprising: aninflatable balloon having a balloon body portion defining a balloonworking length and an un-inflated diameter and a working diameter; and afrangible cover covering at least a portion of the balloon body portionand being operable such that the inflatable balloon having a balloondiameter vs. balloon pressure profile in which a first intermediateinflated diameter and a final inflated diameter of a balloon aredefined, wherein the inflatable balloon attains the first intermediateinflated diameter at a first predetermined pressure, and attains thefinal inflated diameter at a final predetermined pressure that is lowerthan the first predetermined pressure, and the frangible cover beingoperable to rupture under an internal pressure before the rupture of theballoon.
 2. The catheter balloon assembly of claim 1, wherein thefrangible cover is operable to control the balloon to open to anintermediate length that is less than the working length.
 3. Thecatheter balloon assembly of claim 1, further comprising a plurality offrangible covers each being operable to control the balloon to opensequentially to a different larger intermediate diameter that is smallerthan the working diameter.
 4. The catheter balloon assembly of claim 1,wherein the frangible cover is operable to allow the balloon to have asubstantially uniform diameter long the working length of the balloon.5. The catheter balloon assembly of claim 1, wherein the balloonincreases in diameter substantially uniformly along the working lengthof the balloon after the rupture of the frangible cover.
 6. The catheterballoon assembly of claim 1, further comprising: an outer cover coveringat least a substantial portion of the frangible cover operable tocontain the frangible cover once the frangible cover ruptures.
 7. Thecatheter balloon assembly of claim 1, wherein the balloon is a compliantballoon.
 8. The catheter balloon assembly of claim 1, wherein theballoon is a non-compliant balloon.
 9. The catheter balloon assembly ofclaim 6, the balloon comprising two opposed balloon leg portions thatare each integrally connected to a balloon taper portion, with each ofthe balloon taper portions connected to a balloon body portiontherebetween, the balloon working length defined as the length of theballoon body portion of the balloon that comprises an approximate lengthbetween opposed balloon taper portions; further comprising a ballooncover comprising: a first legged cover portion including a first coverbody portion integrally connected to a first cover taper portion,further including a first cover leg portion located at an apex of thefirst cover taper portion, the first cover body portion being operableto overlay a portion of the balloon body portion, the first cover taperportion being operable to overlay a portion of the balloon taperportion, the first cover leg portion being operable to allow the legportion of the balloon to pass through; and a second legged coverportion including a second cover body portion integrally connected to asecond cover taper portion, further including a second cover leg portionlocated at an apex of the second cover taper portion the second coverbody portion being operable to overlay a portion of the balloon bodyportion, the second cover taper portion being operable to overlay aportion of the balloon taper portion, the second cover leg portion beingoperable to allow the leg portion of the balloon to pass through, thefirst cover taper portion and the second cover taper portion are locatedat opposite ends of the balloon cover, the first legged cover portionand the legged second cover portion are coaxially aligned and overlaythe balloon such that at least a portion of the first cover body portionoverlays at least a portion of the second cover body portion, thefrangible cover overlaying the first cover body portion, the secondcover body portion, and at least a portion of each of the first covertaper portion and the second cover taper portion, the outer cover coversthe frangible cover and is coupled to the first cover leg portion andthe second cover leg portion.
 10. The catheter balloon assembly of claim9, wherein the balloon cover comprises a fibrillated material.
 11. Thecatheter balloon assembly of claim 10, wherein the fibrillated materialis ePTFE.
 12. The catheter balloon assembly of claim 11, wherein fibrilsin said ePTFE are oriented in a radial direction.
 13. The catheterballoon assembly of claim 9, wherein the balloon cover is made fromstrips of ePTFE that are adhered to each other.
 14. The catheter balloonassembly of claim 13, wherein the strips are laid in multiple angularorientations on the working length of the balloon and the first covertaper portion and second cover taper portion.
 15. The catheter balloonassembly of claim 9, wherein the balloon cover is adhered to theballoon.
 16. The catheter balloon assembly of claim 9, wherein the firstand second cover body portions that overlap for a substantial portion ofthe balloon body portion also cover a portion of balloon taper portion.17. The catheter balloon assembly of claim 9, wherein a working diameterof the balloon cover is smaller than the working diameter of theballoon.
 18. A method of making a catheter balloon, comprising providinga balloon assembly operable to provide a balloon diameter vs. balloonpressure profile generally depicting a balloon inflation sequenceproviding a first intermediate inflated diameter of a balloon and amaximum inflated diameter of the balloon attained subsequent to thefirst intermediate inflated diameter, the maximum inflated diameterbeing greater than the first intermediate inflated diameter, such thatthe balloon attains the first intermediate inflated diameter at a firstpredetermined pressure, and then further inflates toward the maximuminflated diameter at a second predetermined pressure that is lower thanthe first predetermined pressure.
 19. The method of claim 18, whereinthe balloon has a balloon body portion defining a balloon workinglength, an uninflated diameter, and the maximum inflated diameter, themethod further comprising: covering at least a portion of the balloonbody portion with a frangible cover, the frangible cover being operableto rupture under an internal pressure before a rupture of the balloon;and covering at least a substantial portion of the frangible cover withan outer cover, the outer cover operable to contain the frangible coveronce the frangible cover ruptures during use.
 20. The method of claim18, further comprising providing a first frangible cover operable tocontrol the balloon to inflate to the first intermediate inflateddiameter and a second frangible cover operable to control the balloon toinflate to a second intermediate inflated diameter, wherein the secondintermediate inflated diameter is smaller than the maximum inflateddiameter.